A vertical cavity surface emitting laser has a configuration of a cavity comprising an active layer made of GaAs and GaInAs sandwiched by a mirror above the active layer and an underlayer mirror on the substrate side beneath the active layer. In comparison with an edge emitter semiconductor laser, the length of the cavity is extremely short. It is thus necessary to make laser oscillation easy to generate by setting the reflectivity of each of the mirrors at a very high value of equal to or greater than 99%. For this reason, a distributed Bragg reflector (DBR) is normally used as a mirror. The distributed Bragg reflector is created from layers of low-refractivity materials made of AlAs and layers of high-refractivity materials made of GaAs. The low-refractivity and high-refractivity materials are stacked on each other alternately with a period of 1/4 of the wavelength.
The vertical cavity surface emitting laser is expected to be a key device for realizing large capacity optical communication by transmitting optical information in parallel through a plurality of laser devices arranged in an array. A mounting technology for interconnecting an array of these surface emitting lasers with a suitable array of optical fibers has become an area of study and development. One exemplary mounting arrangement is disclosed in U.S. Pat. No. 5,912,913 issued to M. Kondow et al. on Jun. 15, 1999. In this arrangement an array of surface emitting lasers are disposed on a first module and an array of optical fibers are positioned within a single large opening formed through a second module. There is no attempt to provide individual fiber-to-device alignment in the Kondow et al. arrangement, and it is presumed that the fiber array disposed within the opening will generally align with the laser array upon attachment of the two modules. In the case of an optical fiber having a core diameter of 50 .mu.m and a device also having an optical emission diameter on the order of 50 .mu.m, by setting the gap between the optical fiber and the laser at a value less than or equal to 10 .mu.m, the Kondow et al. arrangement provides a coupling efficiency of only 50%.
An alternative arrangement that provides for improved alignment between an individual surface emitting laser and optical fiber is disclosed in U.S. Pat. No. 5,796,714 issued to T. Chino et al. on Aug. 18, 1998. In this arrangement, the laser substrate itself is etched through on the backside to create an opening (i.e., etch a via through a portion of the substrate material) for the optical fiber. While it is possible to provide improved alignment with this configuration, such an arrangement becomes problematic when utilized with an array of surface emitting lasers. In particular, any mismatch in forming the array of optical fiber vias not only results in misalignment between the lasers and the fibers, but since the vias are formed through the actual optical substrate, requires the entire array to be discarded, a costly and time-consuming result in a large volume manufacturing environment.
Thus, a need remains in the art for a packaging arrangement capable of providing an efficient and accurate alignment between an array of surface emitting lasers and an array of optical communication fibers.